1. Field of the Invention
The present invention relates to an apparatus for performing copying by using an improved optical system.
2. Description of the Prior Art
Known is a copying apparatus having a photosensitive drum, a focusing optical system for leading reflected light from an original image onto the photosensitive drum, an original lighting means, a detection means for detecting the quantity of reflected light from the original image, and a control means for controlling the quantity of light from the original lighting means on the basis of the detected quantity of reflected light. In this known copying apparatus, it has been widely performed to insert a yellow filter into the focusing optical system for the purpose of improving the density of blue color reproduction. In this case, however, there has been a problem with color reproducibility of originals of colors other than blue (mainly, originals of a magenta group color). Further, in the case of using a sheet-like transmission-type filter, there has been a problem that resolving power is apt to be lowered by the reduction in optical performance due to curling.